The mechanical function of the heart is governed by the contractile properties of the cells, the mechanical stiffness of the muscle and connective tissue, and the pressure and volume loading conditions on the organ. The mechanical function for the micro- and macroanatomical twisting motion of the beating heart. The purposes of this are: To examine the terms that are traditionally used to describe mechanical stresses and strain within the ventricle, to explore the three-dimensional organization of cardiomyocytes that influences global ventricular function, to apply mechanical measures to both single cardiomyofibrils and the intact ventricle and to evaluate mathematical and computer models used to characterize cardiac mechanics